726 research outputs found
The dwarf low surface brightness population in different environments of the Local Universe
The nature of the dwarf galaxy population as a function of location in the
cluster and within different environments is investigated. We have previously
described the results of a search for low surface brightness objects in data
drawn from an East-West strip of the Virgo cluster (Sabatini et al., 2003) and
have compared this to a large area strip outside of the cluster (Roberts et
al., 2004). In this talk I compare the East-West data (sampling sub-cluster A
and outward) to new data along a North-South cluster strip that samples a
different region (part of sub-cluster A, and the N,M clouds) and with data
obtained for the Ursa Major cluster and fields around the spiral galaxy M101.
The sample of dwarf galaxies in different environments is obtained from uniform
datasets that reach central surface brightness values of ~26 B mag/arcsec^2 and
an apparent B magnitude of 21 (M_B=-10 for a Virgo Cluster distance of 16 Mpc).
We discuss and interpret our results on the properties and distribution of
dwarf low surface brightness galaxies in the context of variuos physical
processes that are thought to act on galaxies as they form and evolve.Comment: 10 pages, 3 figures, to appear in "Dark Galaxies and Lost Baryons",
IAU244 conference proceeding
New UBVRI colour distributions in E-type galaxies I.The data
New colour distributions have been derived from wide field UBVRI frames for
36 northern bright elliptical galaxies and a few lenticulars. The classical
linear representations of colours against log r were derived, with some
improvements in the accuracy of the zero point colours and of the gradients.
The radial range of signicant measurements was enlarged both towards the
galaxian center and towards the outskirts of each object. Thus, the "central
colours", integrated within a radius of 3", and the "outermost colours"
averaged near the mu_V = 24 surface brightness, could also be obtained. Some
typical deviations of colour profiles from linearity are described.
Colour-colour relations of interest are presented. Very tight correlations are
found between the U-V colour and the Mg2 line-index, measured either at the
galaxian center or at the effective radius.Comment: 34 pages, 10 figures, to appear in A&A journa
A Correlation between Galaxy Light Concentration and Supermassive Black Hole Mass
We present evidence for a strong correlation between the concentration of
bulges and the mass of their central supermassive black hole (M_bh) -- more
concentrated bulges have more massive black holes. Using C_{r_e}(1/3) from
Trujillo, Graham & Caon (2001b) as a measure of bulge concentration, we find
that log (M_bh/M_sun) = 6.81(+/-0.95)C_{r_e}(1/3) + 5.03(+/-0.41). This
correlation is shown to be marginally stronger (Spearman's r_s=0.91) than the
relationship between the logarithm of the stellar velocity dispersion and log
M_bh (Spearman's r_s=0.86), and has comparable, or less, scatter (0.31 dex in
log M_bh), which decreases to 0.19 dex when we use only those galaxies whose
supermassive black hole's radius of influence is resolved and remove one well
understood outlying data point).Comment: 7 pages, 1 table, 2 figures. ApJ Letters, accepte
Initiating a Mexican wave: An instantaneous collective decision with both short and long range interactions
An interesting example for collective decision making is the so-called
Mexican wave during which the spectators in a stadium leap to their feet with
their arms up and then sit down again following those to their left (right)
with a small delay. Here we use a simple, but realistic model to explain how
the combination of the local and global interactions of the spectators produces
a breaking of the symmetry resulting in the replacement of the symmetric
solution -- containing two propagating waves -- by a single wave moving in one
of the two possible directions. Our model is based on and compared to the
extensive observations of volunteers filling out the related questionnaire we
have posted on the Internet. We find that, as a function of the parameter
controlling the strength of the global interactions, the transition to the
single wave solution has features reminiscent of discontinuous transitions.
After the spontaneous symmetry breaking the two directions of propagation are
still statistically equivalent. We investigate also how this remaining symmetry
is broken in real stadia by a small asymmetrical term in the perception of
spectators.Comment: Main text: 12 pages, 3 figures. Appendices: 18 pages (incl. answers
from online survey on Mexican waves). Supplementary website:
http://angel.elte.hu/localgloba
Phase transitions in social sciences: two-populations mean field theory
A new mean field statistical mechanics model of two interacting groups of
spins is introduced and the phase transition studied in terms of their relative
size. A jump of the average magnetization is found for large values of the
mutual interaction when the relative percentage of the two populations crosses
a critical threshold. It is shown how the critical percentage depends on
internal interactions and on the initial magnetizations. The model is
interpreted as a prototype of resident-immigrant cultural interaction and
conclusions from the social sciences perspectives are drawn
Morphological classification and structural parameters for early-type galaxies in the Coma cluster
We present the results of an isophotal shape analysis of three samples of
galaxies in the Coma cluster. Quantitative morphology, together with structural
and photometric parameters, is given for each galaxy. Special emphasis has been
placed on the detailed classification of early-type galaxies.
The three samples are: i) a sample of 97 early-type galaxies brighter than
m = 17.00 falling within one degree from the center of the Coma cluster;
these galaxies were observed with CCD cameras, mostly in good to excellent
resolution conditions; ii) a magnitude complete sample of 107 galaxies of all
morphological types down to m = 17.00 falling in a circular region of 50
arcmin diameter, slightly offcentered to the North-West of the cluster center;
the images for this and the next sample come from digitized photographic
plates; iii) a complete comparison sample of 26 galaxies of all morphological
types down to m = 16.05 (or m 17.5), also in a region of 50
arcmin diameter, but centered 2.6 degrees West of the cluster center.
The reliability of our morphological classifications and structural
parameters of galaxies, down to the adopted magnitude limits, is assessed by
comparing the results on those galaxies for which we had images taken with
different instrumentation and/or seeing conditions, and by comparing our
results with similar data from other observers.Comment: 22 pages, including 4 figures and 4 tables, uuencoded, gzipped
postscrip
Biochemical characterization, molecular cloning and localization of a putative odorant-binding protein in the honey bee Apis mellifera L. (Hymenoptera: Apidea)
AbstractA honey bee antennal water-soluble protein, APS2, was purified and characterized as the first Hymenoptera putative odorant-binding protein. Comparison of its measured Mr (13â695.2±1.6) to that of the corresponding cDNA clone shows it does not undergo any post-translational modification other than a 19-residue signal peptide cleavage and formation of three disulfide bridges. These biochemical features are close to those of Lepidoptera odorant-binding proteins. In situ hybridization experiments demonstrated its specific expression in olfactory areas. Based on its higher expression in the worker than in the drone, ASP2 might be more involved in general odorant than in sex pheromone detection
Ising model with memory: coarsening and persistence properties
We consider the coarsening properties of a kinetic Ising model with a memory
field. The probability of a spin-flip depends on the persistence time of the
spin in a state. The more a spin has been in a given state, the less the
spin-flip probability is. We numerically studied the growth and persistence
properties of such a system on a two dimensional square lattice. The memory
introduces energy barriers which freeze the system at zero temperature. At
finite temperature we can observe an apparent arrest of coarsening for low
temperature and long memory length. However, since the energy barriers
introduced by memory are due to local effects, there exists a timescale on
which coarsening takes place as for the Ising model. Moreover the two point
correlation functions of the Ising model with and without memory are the same,
indicating that they belong to the same universality class.Comment: 10 pages, 7 figures; some figures and some comments adde
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